I'm not aware of a way to switch from the Windows screen to the Applications screen, but there are ways to launch applications and switch windows using the keyboard in gnome-shell.
Alt-Tab
Your question only mentions the Activites pane, but I'll mention this method for completeness, and because it most closely matches the behaviour of several other environments: To switch between applications, use Alt+Tab. To switch between multiple windows of the same application, use Alt+`. Note for non-US-keyborad users: To switch between multiple windows of the same application, use Alt+key above Tab.
Searching in the Activities pane
The "type to search" field in the top right of the Activities pane is one of my favourite parts of gnome-shell. To launch an application without touching the mouse, press the "Win key" (here I'll call it Super) and type the first few letters of the application's name. A list of applications matching your text will appear. Use the up and down arrows to highlight the one you want, and press Enter. For example, if I press Super and type "libr", the applications in the LibreOffice suite are listed for me, and I can select one.
The same method applies to switching windows: if you select an application that's already running, the shell will switch you to that application instead of opening a new instance of it. For example, if I already have Firefox open, and it press Super and type "firef" and press Enter, I get one of my existing Firefox windows instead of a new one.
So what if you want a new instance of an application that's already running? Select the application you want and press Ctrl+Enter.
The Window Navigator extension
This is an extension that allows you to select windows in the activities pane using keystrokes instead of mouse clicks.
These instructions explain how to enable a PPA with some gnome-shell extensions. The relevant commands are as follows:
sudo add-apt-repository ppa:ferramroberto/gnome3
sudo apt-get update
sudo apt-get install gnome-shell-extensions-windows-navigator
After installing, restart gnome-shell (Alt+F2, type "r" and press Enter). If you use gnome-tweak-tool, you may need to launch it and enable the Window Navigator extension under Shell Extensions.
Once the extension is installed and enabled, you can hold Alt in the Activities pane to see a number hover over each window. Press a number key to switch to its corresponding window.
Update
There are plenty of other tips and explanations in the Gnome Project's GnomeShell Cheat Sheet.
xmodmap solution
I think you can do this using xmodmap, a tool to modify keymaps. Since my keyboard does not have a right Super key I cannot confirm this solution, so please leave a comment if it doesn't work.
All steps are done in a terminal
Print the current modifier map
Run
xmodmap
This should print the current modifier map which should like something like this
xmodmap: up to 4 keys per modifier, (keycodes in parentheses):
shift Shift_L (0x32), Shift_R (0x3e)
lock
control Control_L (0x25), Control_R (0x69)
mod1 Alt_L (0x40), Meta_L (0xcd)
mod2 Num_Lock (0x4d)
mod3
mod4 Super_L (0x85), Super_R (0x86), Super_L (0xce), Hyper_L (0xcf)
mod5 ISO_Level3_Shift (0x5c), Mode_switch (0xcb)
The important line is the mod4
line, this line shows which key codes are mapped to the Super_L and Super_R key symbols.
Backup the key map
Before we change anything it is a good idea to backup the current key map, we can do this with
xmodmap -pke > ~/.xmodmap.orig
Now if anything goes wrong you can simply type
xmodmap ~/.xmodmap.orig
to restore your original key map. (If you made some serious mistakes and you cannot properly type anymore, a reboot also works)
Check current key map for the Super keys
Assuming that the Super keys have consecutive key codes (0x85 and 0x86 in this case) we can check the current mapping by running
xmodmap -pke | grep -wA1 $((0x85))
were of course you should change the 0x85 by the key code you have from your modifier map. This should give you
keycode 133 = Super_L NoSymbol Super_L
keycode 134 = Super_R NoSymbol Super_R
( the $((0x85))
converts the hexadecimal number to decimal)
Copy the behavior of the left Super to the right Super
As you can see from the previous step the right Super key has key code 134 but we want it to have the behaviour of the left Super key which has keycode 133. We can do this by remapping the key using
xmodmap -e "keycode 134 = Super_L NoSymbol Super_L"
Checking if it works
If you now do
xmodmap -pke | grep -wA1 $((0x85))
you should see
keycode 133 = Super_L NoSymbol Super_L
keycode 134 = Super_L NoSymbol Super_L
meaning that both keys now have the same behavior. Also the modifier map should have changed on the line with mod4
, we can check this by running
xmodmap | grep 'mod4'
which should give
mod4 Super_L (0x85), Super_L (0x86), Super_L (0xce), Hyper_L (0xcf)
And of course the shortcuts which you mentioned should work too!
Make mapping persistent
If it works, you can make sure that these settings are automatically applied when you boot. Run
echo 'keycode 134 = Super_L NoSymbol Super_L' >> ~/.xmodmaprc
to store your custom key mapping in the file ~/.xmodmaprc
. Run
echo 'xmodmap ~/.xmodmaprc' >> ~/.xsessionrc
to make sure the custom key map is executed when your window manager loads.
Best Answer
I don't know what the root cause might be, but as a workaround I'd suggest hitting Alt+F2 (to bring up the "run" dialog), enter
r
and hit Enter. This will restart Gnome shell, but leave your applications running.